The structure and function of the proteins of the paramyxovirus SV5 will be investigated with particular emphasis on studying the fusion (F), the hemagglutinin-neuraminidase (HN) and the V proteins. The paramyxoviruses are the etiological agents of many biologically and economically important diseases of human beings and lower animals. To understand the different requirements for fusion among paramyxoviruses, an examination of a physical association between F and HN in both cells and virions will be performed for SV5, NDV and HPIV-3 using cross-linking and immunoprecipitation procedures. It will be determined if an association between F and HN occurs in a living cell by tagging F or HN with an intracellular endoplasmic reticulum retention signal. To understand the differences in the role of HN in fusion of SV5, NDV and HPIV-3 kinetics and extent, fusion will be quantified by using membrane fusion and content mixing. An examination will be performed of the fusion properties of a glycolipid anchored F protein (GPI-F) to understand the role of the transmembrane domain in fusion. An investigation will be made of a putative conformational change in the F protein to render it fusion competent. The applicant will determine if there is a cellular receptor for the SV5 F protein and if so, will characterize the moiety. The coordination of zinc by the V protein, the unusual RNA binding protein of SV5, will be elucidated using site-specific mutagenesis and a novel 199Hg NMR technique. The specificity of RNA binding by the SV5 V protein will be determined. The protein-protein interactions of the SV5 V protein will be investigated, including mapping the domain of interaction of the V protein with the NP protein. An investigation will be made of possible interactions of the V protein with cellular proteins.